Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$70.76	11.315%	$78.7665	$78.77	$78.75	$78.80
Purchase #2	$95.39	5.501%	$100.6374	$100.64	$100.65	$100.60
Purchase #3	$158.51	5.780%	$167.6719	$167.67	$167.65	$167.70
Purchase #4	$199.55	3.345%	$206.2249	$206.22	$206.20	$206.20
Purchase #5	$51.99	11.349%	$57.8903	$57.89	$57.90	$57.90
Purchase #6	$8.70	11.721%	$9.7197	$9.72	$9.70	$9.70
Purchase #7	$92.48	7.441%	$99.3614	$99.36	$99.35	$99.40
7 purchase totals =	$677.38		$720.2721	$720.27	$720.20	$720.30